1. Field of the Invention
The present invention relates to a toner for use in recording processes, such as electrophotography, electrostatic recording, magnetic recording, and toner jetting. The present invention also relates to a toner particle producing method.
2. Description of the Related Art
Recently, in laser printers and copying machines utilizing electrophotography, a process speed has been increased at a fast pace, and a toner superior in development performance, transferability, and low-temperature fixation ability has been demanded. In particular, because the low-temperature fixation ability contributes to saving of power consumption, it is regarded as an essential factor in recent research and development of toners of the type that is strongly required to be adapted for environment countermeasures.
Meanwhile, with increasing market expansion of laser printers and copying machines, toners have been demanded to exhibit satisfactory performance even in storage and use under high-temperature and high-humidity environments. Further, the temperature in an apparatus tends to rise due to fanless design in a body of the apparatus with the view of realizing more downsizing and quieting of the apparatus. For that reason, toners have been required to have higher heat resistance as well.
To achieve improvements in development performance, transferability, low-temperature fixation ability, and heat resistance all together, a toner having the so-called core shell structure has been studied in the past. That type toner is designed such that a surface layer of a toner particle has heat resistance and durability, and that an inner layer of the toner particle has the low-temperature fixation ability.
For providing a toner that can realize an image with a high glossiness even in low-temperature fixing and that has high durability even under severe use conditions, Japanese Patent Laid-Open No. 2008-268366 discloses the toner in which a vinyl-based polar resin having a certain acid value and having low molecular weight is interposed between a core and a shell. Japanese Patent Laid-Open No. 5-150549 discloses a method of producing a suspension-polymerized toner, which includes a step of, when the toner is produced by a suspension polymerization method, adding a resin that has an SP (Solubility Parameter) value of 9.0 to 15.0 ((cal/cm3)1/2) and has a higher glass transition point than a binding resin. Japanese Patent Laid-Open No. 2008-064837 discloses a toner of the core shell structure having a core covered with one ore more shells, in which one of shell layers contains wax and the difference between an SP value of a resin exhibiting a maximum SP value among resins, which form the shell layers, and an SP value of a binding resin is 0.20 to 0.70 ((cal/cm3)1/2) or less.